The present invention relates to precast parts joint structure and a method of joining the parts, and more particularly to a method of joining precast aluminum parts, for example, wherein the joined structure is used in an inlet-air surge tank, air surge tank or intake manifold.
Conventionally, since an inlet-air surge tank, an air surge tank and an intake manifold are hollow products formed in a complicated shape having many undercut portions, it has been difficult to form these structures integrally by die-casting using internal cores.
A method of forming a structure such as the inlet-air surge tank or the like, according to which two divisional pieces are preformed by die-casting and then bonded with each other by using epoxy group adhesives, has been proposed in Japanese early patent application publication No. 60-45771.
When the two die-cast pieces are bonded with each other by using the above-mentioned adhesives, the surfaces to be joined are supplied with adhesives, and then the surfaces are fastened by, for example, bolts. However, the layer of adhesives cannot be made uniform in thickness when the bolts are fastened. In particular, the adhesive layer becomes thinner near the bolts-fastening portions than in other portions. For example, the adhesive layer may be 0.3 mm thick in some portion and 0.02-0.05 mm thick in other portions. As a result, there are problems in obtaining sufficient bonding strength. Also, peeling-off may occur easily.
Conventionally, then, in order to provide a uniform adhesive layer, spacer plates (for example 0.1 mm in thickness) have been inserted. However, this method is disadvantageous not only in that a number of spacer plates are required, but also in that the step of inserting the spacer plates becomes necessary. Further, there is no adhesive layer where the spacer plates are inserted, so that sufficient bonding strength cannot be obtained.